The instant application relates to hydrogen cooled hydrogen storage units, and more specifically to a unit which provides excellent heating and cooling thereof while also providing for a high packing density of the storage materials therein and encapsulation of the storage materials to prevent entrainment into the high speed cooling hydrogen flow therethrough.
The instant patent application describes a hydrogen storage unit useful for a hydrogen-based economy. The storage unit allows for fast cooling and/or heating thereof using gaseous hydrogen as a direct, convective heat transfer medium. The unit provides excellent heating and cooling of the hydrogen storage alloy rods therein while providing for a high packing density of the storage alloy, and encapsulation of the storage alloy to prevent entrainment of the materials within he hydrogen coolant flow. The instant storage unit is useful in a hydrogen based economy.
An infrastructure for such a hydrogen based economy is disclosed in U.S. application Ser. No. 09/444,810, entitled xe2x80x9cA Hydrogen-based Ecosystemxe2x80x9d filed on Nov. 22, 1999 for Ovshinsky, et al. (the ""810 application), which is hereby incorporated by reference. This infrastructure, in turn, is made possible by hydrogen storage alloys that have surmounted the chemical, physical, electronic and catalytic barriers that have heretofore been considered insoluble. These alloys are fully described in copending U.S. patent application Ser. No. 09/435,497, entitled xe2x80x9cHigh Storage Capacity Alloys Enabling a Hydrogen-based Ecosystemxe2x80x9d, filed on Nov. 6, 1999 for Ovshinsky et al. (the ""497 application), which is hereby incorporated by reference.
Hydrogen storage units have a number of requirements. First and foremost, they are required to be able to store hydrogen. This bare minimal requirement is met by many prior art storage units. However, to be commercially useful in a hydrogen based economy, the hydrogen storage unit requires many more properties. One requirement is a high specific capacity hydrogen storage material. Such materials were invented by Stanford R. Ovshinsky et al and are disclosed in the ""497 application. Another requirement is a unit which has a high volumetric and gravimetric packing density of storage materials. One such unit is also disclosed in the ""497 application.
A further requirement is a unit that has the ability to be cooled a high rate. This is required to be able to quickly charge hydrogen into the unit while maintaining proper operating temperature by removing the heat of hydride formation. The instant inventors have determined that maximal cooling using minimal hardware can me achieved using excess hydrogen flow though the system to remove the heat. A system which employs hydrogen cooling is also disclose in the ""497 application.
In addition to being able to quickly and efficiently cool the hydrogen storage materials within the storage unit, the hydrogen storage materials must be heated quickly and efficiently to release hydrogen therefrom during use. To accomplish this, there must be efficient thermal transfer from the source thereof through the bulk of the storage material. While most systems will transfer this heat, they do not do so efficiently.
Finally, for many applications ease of capacity expansion is a must. While many prior art systems do not allow for expansion, some do. However, with most systems, expansion of the amount of hydrogen storage materials reduces the cooling and heating efficiency.
Therefor, what is needed in the art is a high capacity hydrogen storage unit having high volumetric and gravimetric storage capacity (i.e. high packing density of storage materials), which is capable of being cooled at a high rate, is capable of efficient heat transfer from an internal heat source throughout the storage material, and is expandable without losing any of the aforementioned properties.
The instant invention is a hydrogen-cooled hydrogen storage unit. The unit employs excess hydrogen flow between hydrogen storage alloy rods in the hydrogen storage unit in order to provide convective cooling thereof. The unit provides for high packing density of the storage materials. The unit also allows for efficient thermal transfer of heat energy from a central source of heat through the rods thereof during discharge of the stored hydrogen. The hydrogen storage rods of the unit are encased in an encapsulant layer which prevents entrainment of the hydrogen storage material in the high flow rate hydrogen.
The hydrogen gas cooled hydrogen storage unit includes a plurality of encapsulated hydrogen storage alloy rods disposed within a storage unit casing. The unit also includes a hydrogen flow channel region between and around the hydrogen storage alloy rods. The flow channel region provides for pathways between the rods to allow for high speed hydrogen gas flow. A portion of the hydrogen is stored within the storage material and releases its heat of hydride formation. The remainder of the hydrogen flows through the hydrogen flow channels at a sufficient mass flow rate to remove the heat of hydride formation.